Fused electrical plug



, March 21, 1933. L. MAXAM FUSED ELECTRICAL PLUG Filed April 10 FIE-Patented Mar. 21, 1933 UNITED STATES PATENT OFFICE LEONARD L. mm, 01 LOSANGELES, CALIFORNIA, ASSIGNOR OF ONE-THIRD TO CLARENCE S. CREWS, OF SANPEDRO, CALXII'ORNIA FUSEID ELECTRICAL PLUG 7 Application filed April 10,1931. Serial No. 529,115.

This invention relates to electrical equipment, and has for an objectthe provision of an improved type ofelectrieal plug for use in.releasably connecting a flexible conductor to the terminals of anelectrical socket which also may be carried by a flexible conductor, orwhich may be disposed within a rigid structure such as a floor, or wall.1

A more detailed object is the provision of 10 an electrical plug of thegeneral character de-' scribed, which is capable of making or breaking aplurality of electrical circuits simultaneouslv.

A further object is the provision of an elec- 16 trical plug which isadapted to maintain a predetermined polarity of the oppositeconductorsof a circuit, i. e., a plug in which means are provided forpreventing the insertion of the plug within its socket, in any 20 mannerother than that which will result in a predetermined polarity vof theconductors to which the plug is secured.

A further object is the provision of an electrical plug as described, inwhich fuses are interposed between the conductors and the contacts ofthe plug, these fuses being car ried within the body of the plug itself.

A still further object is the provision of a plug, wherein means areprovided for attaching the conductors to the plug, in such a manner thata considerable force may be imposed upon the plug to remove it from itssocket, this force being in the nature of tension upon the conductor,and still avoid any possibility of severing the connection of theconductors to the plug.

A still further object is the provision of an electrical plug asdescribed, in which means are provided for resiliently pressing thecontacts of the plug against those of the socket when the plug ispositioned operatively therein.

A further object is to provide means for locking the plug within itssocket, preventing accidental removal of the plug, and requiring theexertion of conscious effort on the part of the operator, to remove theplug.

The invention possesses other objects and advantageous features, some ofwhich, with those enumerated, will be set forth in the followingdescription of the inventicns particular embodiment which is illustratedin the drawing accompanying and forming a part of the specification. I

Referring to the drawing Fig. 1 is a perspective View of a plugincorporating the principles of the present invention, and showing thecover with which the plug is provided, moved to open position so as tobetter disclose the nature of the invention.

Fig. 2 is a vertical transverse sectional View. The plane of section isindicated by the line 22 of Fig. 1, and the direction of view by thearrows.

Fig. 3 is a perspective view of the plug pushed partially into itscooperative socket, to better disclose the manner of the plugsemployment. Portions of the figure are broken away to reduce its size.

Fig. 4 is a horizontal sectional View taken upon the line 44 of Fig. 3,with the direction of view as indicated.

The plug of the present invention has been designed with the especialobject in View of 7 providing convenient means for establishing thecircuits whereby the reproducing unit of a dynamic loud speaker isenergized, and more especially for use in conjunction with that type ofsound reproducing instrument which is employed to reproduce soundsaccompanying action depicted cinematographically. However, it should beunderstood that the plug is adaptable to practically universal usage,and may be employed wherever 85 it is desired to provide means forquickly establishing and breaking one or more electrical circuits.

It should be pointed out by way of explanation of the use to which theplug of the pres 90 cut invention is put, that loudspeakers of thegeneral class indicated hereinabove require two circuits, to-wit: thefield circuit or the circuit associated with the field coil of thereproducing unit, and the talking circuit or 95 the circuit whereby themoving coil of the speaker is energized. In stage installation, it hasbeen customary to interpose fuses within the field circuit, inasmuch asthis circuit ordinarily carries a considerably greater quantity p 'ofcurrent than the talking circuit. 'I Iowever,

in all installations of which I am at present aware, it has beencustomary to provide these fuses in a separate wall box, or otherconvenient location; and inasmuch as the socket within which the plug isto be positioned in order to ener ize the loud speaker of a tall;-

' ing moving picture installation, is ordinarily placed in the fioor ofthe stage, Closely behind the pro ection screen, the fuse-box and thesocket are ordinarily some distance apart,

I resulting in considerable inconveniencewhenever the necessity arisesfor replacing a fuse.

Another feature in connection with the field and talking clrcuits of adynamic loud speak- I posed of any suitable dielectric material such asfiber or its equivalent. A projection 7, preferably of reduced width,extends from the lower end of the body 6, and is provided withpreferably a pair of spaced slots 8 both slots being in the same side ofthe projection 7 As is clearly indicated upon Fig. 2, the bottom 90feach of the slots 8, instead of being parallel to the sides of the plug,inclines from the bottomell ofthe plug, upward and toward that sidethereof in which the slots 8 are dis posed. A contact 12 of suitableconductive material, is secured to the bottom 9 of each of tie slots 8,in any suitable manner, such as by countersunk screws 13 threaded intothe material of which the body 6 is composed.

A recess 14 is formed in the body 6, in registry with the upper end ofeach of the slots 8, preferably the bottom of each recess 14 being'ofiset from the bottom 9 of the associated slot 8, as clearly s iownupon Fig. 2 The up-. per end of each of the contacts 12 is sigmoidal inconfiguration, so as to dispose the extreme upper end 16 against thebottom of the asso ciated recess 14. Wings 18 are formed upon theextreme upper end 16 of each contact, these wings 18 being curvedlaterally in respect to the entire plug assembly, to resiliently graspone of the contact ends 19 of a conventional cartridge fuse 21; with theresult that the extreme upper end 16 of each contact 12 provides aspring clip for resiliently retaining and establishing electricalconnection with one'termin al ot tile fuse 21. A similar spring clip 22is provided in the opposite end of each of the recesses 14, to accommodate the other terminal 23 of the associated fuse 21. Conductors 24are releasably Accordingly, one ofthe fea- I connected to the springclips 22, by means of terminal screws 26 threaded into the clips 22, andextend through the top of the body 6, recesses 27 extending from theupper ends of the recesses 14 to the top of the plug being provided forthe accommodation of these conductors 24.

A second pair of contacts 31 are provlded upon the side. edges of. theextension 7 of the body 6, each contact 3 1'b'eing rigidly attachedthereto'as by screws 32'or their equivalent. Each contact 31 is providedwith a tongue 33 severed therefrom along all but one of its edges, and-defiected outwards slightly, as clearlyshown upon Fig. 1. Each contact31 is also; provided with a terminal screw 34 threaded into theassociated contact 31, or into thematerial of the plugitselfior both. Bymeans of these terminal screws 34, conductors 36 may be releasablyattached to the contacts 31, these conductors 36 extending fromtheshoulders 37 defining the upper end of the projection 7, to the topof the plug,

through recesses 38 spaced from the recesses 27. Preferably, all four ofthe conductors 24 and 36 are gathered intoa single bralded conductor 39,in which the several conductors 24 and 36 are insulated from each other.A clamp 41 is rigidly attached to the conductor 39,- closely adjacentthat point at which the several conductors24 and 36 diverge, the

clamp 41 being firmly secured to the conductor 39, through theexpedient'of its being split at one side thereof, and having screws 42extending through opposed flanges 43; with the result that by tighteningthe screws 42, the flanges 43 may be pressed together to secure theclamp 41 firmly to the conductor 39. The bottom of the clamp 41 isextended laterally,

so that flanges 44 rigid therewith may em- 3 brace three sidesof the topof the plug, screws 46 extendingthrough the flanges 44, so as to rigidlyand removably attach the clamp 41 to the top of theplug- A collar 47,which is connected to the plate48 of the clamp 41 by a chain 49, isclamped upon the multiple conductor 39 in such position that'any tensionimposed upon the conductor 39 will be taken by the chain 49, rather thanby that portion otthe conductor 39 at the point whereit extends out ofthe clamp '41. This arrangement permits removal of theassembled plugfrom its associated socket,'by exerting tension upon theconductor 39,and avoids the liability of severing the connection of one or more oftheconductors 2401' 36, withits associated terminal screw 26 or 34,respectively, and also protects the conductor 39 bypreventing theportionthereof which receives the greatest amount of fiexure, from beingsubjected to tension. I I V A closure 51 is hingedly'attached to thebody portion 6 bya hinge 52, permitting the closure 51 optionally to beswung to open position, as shown upon'Fig; 1, or to closed position, asshown upon Fig. 3, wherein the closure overlies the recesses 14, 27 and38, to effectually conceal the conductors 24 and 36, and the fuses 21with their spring clips 22 and 18. The closure 51 is releasably held inclosed position, through the expedient of hinge knuckles 53 and 54carried by the body 6 and closure 51, respectively, and which move intoalinement when the closure is moved to closed position to receive aremovable pin 56. The closure 51 is also provided with suitable recesses57 and 58 adapted to register with the recesses 27 and 38, respectively,when the clo sure is closed, to better accommodate the conductors 24 and36, respectively.

The plug hereinabove described, is designed primarily for operation inconnection with the conventionalsocket or pocket as it is termed in thetrade, ordinarily employed for theatrical use. Such a socket isindicated in its entirety by the character 61, and is shown as being setflush with the floor 62 of a stage, or with the outer surface of a wall.It is conventionally provided with spaced spring contacts 63 with whichconductors 64- are in communication, these contacts 63 being spacedalong one side of the socket 61, in registration with the recesses 8 ofthe plug 6. The socket 61 is also provided with contacts 66 at the endsof the socket, and with which conductors 67 are in communication. lVhenthe plug 6 is thrust into the socket 61, the upper ends of the contacts63 come into engagement with the contacts 12,

' which, on account of their obliquity, deform the contacts 63 asmovement of the plug '6 into the socket 61 continues. As a result, thecontacts 63 are resiliently pressed against the contacts 12, to insuregood electrical contact, which is also enhanced by the wiping engagementof the contacts 12 with the contacts 63, as inward movement of the plug6 takes place.

Simultaneously with the engagement of the contacts 12 and 63, thecontacts 31 engage the contacts 66. Efiiciency of this electricalconnection is insured by the spring tongues 33 which resiliently pressoutward against the contacts 66 when the plug is in operative position,as will be readily understood.

Means are provided for retaining the plug 6 within its socket 61 againstaccidental removal. A detent in the form of a plate 71 is slidablymounted adjacent the lower end of the plug, and is urged by a spring 72to extend its end into a keeper 73 provided adjacent the bottom of thesocket 61. Hence, the plug cannot be removed unless the plate 71 iswithdrawn against the action of the spring 72 F or this purpose a rod 74is provided, extending from the top of the plug 6 to the plate 71,within which a hole 76 is formed to receive a wedge 77 carried by therod 74. A spring 78 under compression between the top of the plug 6 anda head 79 on the rod 74, normally holds the wedge 77 retracted from thehole 76, so that the spring 72 can 'push the plate 71 into the keeper73, but by depressing the head 79, the wedge may be pushed into the hole76, engaging the plate 71, so as to pull it away from the keeper 73,

whereupon the plug 6 may be pulled out of companying cinematographicdepiction of action. Such sound reproducers require two independentcircuits termed the field 0011 011- cult and the talking circuit. Theconductors 24 of my plug are intended to carry the'field coil circuit,inasmuch as this circuit requires a heavier current than the talkingcircuit. The amount of current flowing through the talking circuit is soslight that no need is. presented for providing fuses therein;consequently, the unfused conductors 36 are intended to convey thecurrent of the talk-ing circuit. The socket 61 is ordinarilyemployed foreach of the sound reproducing devices of a bank or tower of theconventional installation. Ordinarily, there are four loud speakersdistributed about the back of the moving picture screen, andconsequentlv there will be four sockets 61 in the floor 62 of the stage,at a convenient location to permit insertion of a plug 6 within eachsocket 61, it being understood that the conductor- 39 of each plug 6leads to one of the electrical reproducing units of the bank ofspeakers. Obviously. the inclusion of the fuse 21 within the plug,dispenses with the necessity of employing a separate fuse-box.

It is to be understood that the details of the invention as hereindisclosed, are subject to alteration within the spirit or scope of theappended claims.

I claim:

1. An electrical plug comprising a body of insulative material, aplurality of electrical contacts lying entirely within individualrecesses in a common lateral side of the body, and a conductor connectedto each contact.

2. An electrical plug cooperative with a socket having a plurality ofdifferentiated pairs of electrical contacts therein, said plugcomprising a body of insulative material receivable within said socket,a plurality of pairs of electrical contacts carried by said plug anddifferentiated similarly to those of the socket, and means for bringingcontacts of the plug into engagement with the associated contacts of thesocket when the plug is inserted therein.

3. An electrical plug comprising a body of insulative material, aplurality of electrical contacts set within recesses in a common side ofthe body, and arconductor connected to each of said contacts, saidcontacts 'being'incli'ned from the bottom of said plug toward the saidside thereof. i 4:. An electrical plug cooperative with a socket havinga plurality of structurally differentiated pairs of electrical contactstherein, said plug comprising a body'of insulative material receivablewithin said socket, a plurality of pairs of electrical contacts car-.riedby said plug and difi'erentiated similar- 1y to those of thesocket, means for bringing contacts of the plug into engagement with theassociated contacts of the socket when the f 15 plug is insertedtherein, an electrical conductor connected to each of said plugcontacts, means associated with each of said plug contacts forresiliently pressing them against the associated socket contacts, andfuses in- -2 terposed between certain of said conductors and theirassociated contacts.

5. In combination, an electrical plug connector, a socket membertherefor, and releasable means for locking said plug within said 2socket member, said locking means comprising a detent carried by saidplug, means pressing said detent'into extended position wherein saiddetent engages said socket memher, and means operative to withdraw saidzsu detent. r

i 6. An electrical connector comprising a I plug member, a socket memberadapted to re ceive said socket member, contacts carried by saidmembersand adapted to electricalco 1y engage each other when said plug memheris disposed within said socket member, a movable detent carried by oneof said members and adapted to engage the other member to retain theplugmember within the socket so member, and means forwithdrawing saiddetent. V y

In testimony whereof I have signed my name to this specification.

LEONARD L. MAXAM,

